Before assuming that the controller is bad, check to see if you have a master valve. If you have a master valve, water will be shut down to your whole irrigation system when the controller is turned off, so your assesment may be incorrect. It may be as simple as some dirt or a small pepple is in the valve body keeping the valve open. Most valves can be unscrewed by hand for service. If you want to open up a valve to clean it up, just make sure you have the water supply turned off.